Landing information receiving system



Sept. 23, 1952 A. cAsABoNA E-r As. 2,611,892

LANDING INFORMATION RECEIVING SYSTEM med April 17, 194e 9 sheets-sheet 1 INVENTORS fwn/@Nr @M60/VA GLAS 67A W5 f] TTORNZY sept. 23, 1952 Filed April 17, 1948 A. CASABONA ET AL LANDING INFORMATION RECEIVING SYSTEM Sheets-Sheet 2 Sept. 23, 1952- Filed April 17, 1948 LEFT OF COU/95E A. cAsABoNA ET Ai. 2,611,892

LANDING INFORMATION RECEIVING SYSTEM 9 sheets-sheet s 75mm/a RWM/Na TERM/Na 28 TEfM//vm IN VEN TORS /I/vf/o/W c45/45mm G05 5m ws Sept. 23, 1952 A. cAsABoNA r-:T AL 2,611,892

y LANDING INFORMATION RECEIVING SYSTEM Filed April 17, 1948 9 ShebS-Sheet 4 A TTOIFNE Y Sept. 23, 1952 A. cAsABoNA Er Ai. `2,611,892

LANDING INFORMATION RECEIVING SYSTEM Filed April 17, 1948 asheets-sheet e A TTOP/VEY Sept. 23, 1952 Filed April 17, 1948 A. CASABONA ET AL `LANDING INFORMATION RECEIVING SYSTEM 9 Sheets-sheet 7 T TOZPNEY Sept. 23, 1952 A. cAsABoNA E1' AL 2,611,892

LANDING INFORMATION RECEIVING SYSTEM Filed April 17, 1948 9 Sheets-Sheet 8 INVENTORS -ANTf/oA/y Aman/v4 @as smv/s BY ATTORNEY Sept. 23, 1952 A. CASABONA ET AL LANDING INFORMATION RECEIVING SYSTEM ANTHONY IN VEN TORS Cf/noN/l GUS 57A W6 ATTORNEY atentecl Sept. 23, 19.522

j UNITED :STATES PATENT. xo.1=;F1CEfi l f l 2,611,892 A LANDING INFORMATION RECEIVnvG Anthony'Casabona, Hawthorne, and Gus Stavis',

" Ossining, N.V Y., assignors.` to International I Standard Electric Corporation, New York, N; Y.,

a corporation of Delaware Application April 17, 1948,seria1No. 21,654

9 Claims. (Cl. 343-11) This invention relates to radio navigation systems and particularly to an arrangement for determiningthe position of a mobile craitrelative toa givenoourse. 4

Radiant energy systems" for lguiding mobile The above-mentioned and other featuresand objects of the invention will become moreapparent and the invention itself, though @not necessarily defined by said-features andfobjecta,

5 Will be clearly understood by reference to thelfo'lcraft, such 'as aircraft, with respect to a prelowing description of an embodiment `of theinscribed course Yare well known. In locations vention takenin connectionlwith-the accompanywherein "considerable aircraft traffic Vis exing drawings whereim i" i .i perienced, as in connection with the landing of Fig.A 1 shows an arrangement-for"determining aircraft on a runway, it is desirable that the inl0 theposition of aircraft relative to providing landformation given to mobile craft to enable it to ing information; f i 1 `make an instrument landing be reproduced on Fig. `2 shows in block diagramform-Lonere- Athe ground for purposes of monitoringftrafc ceivingA system ifor obtaining 'azimuth-rangemcontrol, and for emergency talk-down procedure. dications offa landing aircraft; Normal operationof ground equipment providing l5 Fig. 3 represents a vectorial analysis'of theop Hthese facilitiesisusually derivedfrom the pulse eration of the system of Fig'QZf; l. f i r f f" response of Yan aircraft, eitherof the cooperative Fig. ishows in block diagramrform-'asecond reorpassive typeuv ceiving system for obtaining azimuthlindications v.An object of this invention is-to provide a novel 0f a landing aircraft; 1. 1 f i arrangementfor processingpulse energy radiated Fig. `5 shows a vectorial analysisoi` theloperafrom a' mobilejcrafttoobtain its position with tion of the systemof Fig. 4; f. f UV of. respect to aprescribed course.V Fig. 6 shows in block di'agran'i'v form a third-re- In accordance with anembodiment of our inceivng system for obtainingzazimuth' indications vention, a receivingsystem for pulseenergy, as of a landing aircraftf n "1; 2., l. for-example, radiant energy pulses radiated from 2o Fig. 7 showsin block .diagramform a fourth a mobile craft such as an aircraft,- Vcomprises twoV -Tecving SYStem for` 0btaningiazimuth .'indicaantennas which are installed onevon--each side of tions of a landingaircraft; :4 V ltagggpt therunway in the vicinity of the pointof` contact Fig 3 ShOWS a receiving. System 'orpobtaining for-landing for providing azimuth tracking of `eleVlJOIl ndiCaOIlSOf a landngarraft; 'tl'reaircraft4 Theantennasare 'spaced apart a 30 Fig. 9 shows a vectorial analysisof theioperadesired faction of a AWave length which detion of the glide path arrangementxof Fig.,8.

termines' the sub-carrier `frequency 'component oi Referring t0 Fig. 1 there is shown a radionavi- "the pulse `envelope ,to be used. The energy from gation system for providing kazimuth .I elevation each antenna is received in individual receivers. 2, andrange, indications of an' aircraft-Lheing u"he output from each antenna after passage 35 `directedgtoa landing on the runwayi.. `'Ilwnanthrough-'prosses of `eombmrig, phasing. and tennasand are providedspacedisymmetricalmodulation by modulating wavesA from al local .1y to each sideof the runway`.int.the vicinityfsof source provides a resultant output in the form 'of the pointof contact; for receivingjradianaenergy modulated sub-carrier energycorresponding to` pulsesradiated from the .aircraftsd ldesrrgzto the time interval of ther-pulsed `output of each 40 make a` landing- Orl,Said,rur'iwayzY ZTheoutputpf of the receivers. Indicating means arethen pro- `antennas 5 and sfoupon processing-mme unitn-1 vided vfor comparing the amplitude of the two yields the' azimuth position of' the craft; The modulations of the modulated sub-.carrier energy elevation position ofA the craftis :obtainedtfroin for obtaining the aircraits azimuth. For prothe outputof two radiatorsspaced apartiverticall; vidingelevationtracking of the aircraftgfan ele- 45 1y, and mounted onpnes'ide offthe runway# In lvationantenna system corresponding to a glide Fig. 1, the elevation antennascomprise antenna@ path" radiation is provided onone side of theruny and `one off the azimuth antennas 26. .The original way. The elevation system comprises .two` an- Source of Athe radiant,.energyi;pulsesfmayibeithe `termas spaced apart in the vertical.- Thepulse aircraft-itselLf-or a ground-'stationy transmitter `energy lreceived by each of said glide path anso System 8A. The ground station may provdemhe Y tennasafter processesl of combining, yand modu# energy, f01" BXaIflDle, in the form oflpulsed'carrer lationby: local modulation Wavesprovides a refrequency energy which'may beradiatedfifrom sultant 'output'which when applied to an indica- OHG 0f the receiving antennasprqfrom @beamed tor-provides the desiredelevation tracking `convammini-2t 0f itrown and is revertedrom' the-'fair'.- tr-n1. 1 i' i- 1- fr -L ffl? 5,5 V,Crgftlto the receivingam-,gnna-S,.mlnam The sub-carrier frequency is derived asa component of the pulse modulation. `By utilizing a ground station for the original source of pulse energy to -be reverted by the aircraft, the range of the craft may also be conveniently obtained.

n Referring ,tofFig .2, there are shown two antennas landt-spaced symmetrically to each side of the runway in the vicinity of the point of contact, for receiving radiant energy pulses radiated from an aircraft desiring to make a landing on said runway. The ground station 8A of Fig. -1

provides pulse modulated carrier frequency energy which is reverted from theaircraft 4, to the receiving antennas' and B'of Fig. 2. The carrier frequency for this system .is of .no concern and can be any frequency adaptable to radar terminals I4 and l5. These need not necessarily be of the same magnitude and, in the analysis,

a ratio of 2 to 1 was chosen for these energies.

Referring to the on-course analysis, the energies at the output terminals of the bridge I'I andH |16 areshown to be in phase. lAfter modulation,

the resulting phase of the carrier and sidebandv components at terminals 28 and 29 is shown. ,A These are mixed and the resulting vector diagram forthe output at terminal3 l shows equal amounts -of 'amplitude and phase modulation of F1 and F2.-

" Although the detector will disregard the phase technique. However, it is desirable that the spacing between the antennas l and 6 be slightly less than a half wave length at the sub-carrier frequency to provide the desired pattern formation. V The energy fromeach antenna 5 and 6 lisfreceivedzinthe individual receivers' and BA, respectively. The carrier .frequency pattern. is

nQtLQdetected. `but thev demodulated pulse output from each receiver is .passed through separate yvideofampliier:circuits I0 and IOA to respective tuned.sub-carrier amplifier circuits AIl and l2 which detect the sub-carriertcomponent of the :pulse lhe pulse repetitionrate and pulsewidth shouldfpreferably be chosen so as-to favor the sub-carrier frequencies. The relativephase of the continuousrwavfegenergy being delivered by each subcarrieraampl-ier is ydetermined vby the .relative timing of the jexcitingfpulsesf. The two sub- .carrier amplifier .outputsfla-re mixed in .a hybrid n type transformer bridgel3 such that'the gener-v igiesbeingdelivered by terminals ylill and l5 are addedatterminal Ig6 and subtracted at .terminal I1. The resultant energy atterminal I6, iafterbeing zphase shifted i90 in circuit I8, is modulated with equal amounts of modulating freq1-lenny :waves Fl 'rand F2 in .modulator [9. 'The .modulatingzrequency waves FI and F2 are derived from a modulating frequencyisource such pacitance l.oscillators .52| .and .22,whose distinct outputs are mixed inLtlre-.mixer circuit 23 in such `azmanner y:wherebytheir sum produces the frequency F.1l :afterfzpassage through. the filter 24 end ftheirldiiference :produces :the frequencyv F2 after' :passage v,through the `filter '25. The

FI .fand F2 .zwaves from the filters z.are .then applied :through .the hybrid :coil Aarrangement 26 l.gierg'fy @at :terminali-3| is detected yin 32, .ltered in fand 134,'fand ydisplayed on across pointer type `meter '35, orxany :other` adaptable indicating 'ide- Janalysisof 'the oper-ation. ofl thesystem is shown vectorially 'in"Fig. 3.' y Assuming' the .airplane-tto be:on'-!cours`e,"the reflected pulses iwill .-larrivefatzantennasfSiand 6 simultaneouslyso that @the sbecarrier frequ'encyappears in phase at modulation,y it is ofinterest to notethat equal i. .amounts exist. Hence an on-'course indication is obtained. .If the levels at terminals I4 and l5 are" adjusted to be equal, then the energy at terminal I1 will be zero and no phase modulation will exist.

When the aircraft is to the left of course, the energy at 5'Will lead the energy at 6. The vector 'analysis shows that under these conditions a predominance of F2 modulationwill produce ,the desired olf-course indication. .Again lsome phase modulation exists because ofthe diierencesin magnitude of the two initial energies. 'When these are equal the vectors will assume orthogonal positions'and the phase `modulation will disappear. The vector t analysis `for vvthe aircraft ,to-,the right of course shows a'predominance .of Fi modulation producing anr oir-course indication toithe opposite side. Hence normal localizer .operation isobtained. I v

The sub-carrier `amplifiers maygbe ,provided with automatic volume control lso as .to maine t tain the energyon both sides 4equal Aas faras possible.v This :AVC may b e operated from aQre'fference level so. that gains on eachside .willedjust themselves for-:equal output. l.

The sharpness/of the system canbefrlcreased by the use of several harmonic frequenciesof the sub-carrier in addition. to .the.subcarrier.

`As mentioned previously, fall that isnecessary i for the operation of `the system is fthatthelaircraft be-illuminatedwith pulsedenerfgy. The

response .received at one antenna, ,suchfaS 15, may

.also be used in an oscilloscope display 36v 'soa'sfftjo detect the presence and range-of'each aircraft in the approachfarea. If .=a sector swepltfrrow beam transmitting antennafis used, .theoscillofsco-pe display may be of the PPI type having t sweep generator S'Itriggered byy a -synchrmiiz ing signal from-the ground transmitter-'8a'. o'ifFig. A1 as .applied `to terminal A38. A frange`r cursor '39 .may be thenl usedtopick outany/aircraftlojr lexample 4 0 in the approach area.` The range gate lIl is coupled toterminal 38 and only :permits the passagey of pulses from the chosenfaircraft 'and its position shownvon the crossgpointerimeteri35. The modulating system maybe-duplicatedfso -fthatseveralaircraftcan be gated inland simultaneous position .readings obtained. In vrthe case of'sectorswept transmission, it is necessary for the indicator', to have persistencysince-,ethe

sweeptime. `i Y lA second `general method iforobtainingv localizer operation is villustrated in Fig. V4. Here, ft'wo l lbridges-."dz'and 43 are used before modulationjain order to iisolate the ,sub-carrier reception patterns. The energyv at l terminal 44, QOI1gtB11lS 15.1.1.6 inf-.phase components `of the Ienergies' pi:`.1 :nrr1 Y)doth sides, f which is representative of one matter!!! Terminal 45. contains an outy of phase component 'from'. both sides and thereforegives ano-therfpat-y tern. When these are :mixed `inszthe second bridge 43, terminals and 41 will deliver equal therequlred on-course indication results. If the aircraft is to either side of the course, terminals 46 and 41 will deliver unbalanced energy alternately and one section will receive more energy than the other. The lower bridge 50 is usedfor combining energy and topreventl crossmodulation. The vector analysis of the system is shown `in Fig. 5, reference being had to the energies at terminals 44-41 and 5l-54. As before, `unequal response of the two stations results in some phase modulation and a subsequentlywider course, but does not shift its position.

Fig. 6 shows a system which is essentially the same as that just described except that the comy bining in circuits 55 and modulating in circuits 56 is done on the pulsed energy before -the pulses excite the sub-carrier amplifier circuits 51. Although this makes it necessary for the bridges 58 and 59 and modulator circuits 56, to be wide band, the advantage is gained that only one sub-c-arrier ampliiier or filter is used, resulting in greater stability of the system. The block diagram of Figure 6 also shows how a harmonic amplifier B0 may be connected in Order to produce a sharper course. The compromise between clearance and sharpness can be effected by adjusting the relative gains of the sub-carrier amplifier 6| and the `harmonic amplifier 50.

The bridges 58 and 59 shown in Fig. 6 may be l.transformer bridges of the type shown in Fig. 2. If wide band video transformers are used, the bridge will pass the pulses essentially undistorted.

. Rot-ating goniometers can be used for the modulating circuits 56 and again these can be made to pass a jv-deo band;

If electronic modulation is desired the system of Fig. '1 may be used. This system is essentially similar to that of Fig. 2 wit-h the exception that .again the combining in circuits "52 and modulation in circuits 63 is accomplished before the pulses excite the sub-carrier amplifier circuits 64, hence :all components before the vamplifier must be wide band.` Delays of 180"` at the sub-carrier frequency 65 and 56 are shown in the mixing circuits 62 but thesev can be replaced by cross-overs or polarity reversals of the `pulse energy. This type of operation would allowthe `use of the wide band transform-er .bridges discussed above. Pulse modulators 51 and operate essentially yas a side band generator.

-'I'.hey are ex-cited out of phase because of delay- 56 and the outputs when mixed will contain only sidebandsof the modulating frequencies. The vector :analysis of the system, therefore, is es. sentially the same as that shown lin Fig. 3.

The block -diagram of Fig. 8 shows a method for obtaining elevation information from pulsed energy reverted from aircraft to be landed. rI'he received energy from the upper and lower antennas 6 and 8 is fed to the two input terminals 69 and 1l) of ya carrier frequency bridge 1l. The output terminals 12 and 13 of the bridge are connected to modulators 14 and 15 so that each output is modulated by FI :and F2 respectively. The energies Aare combined in a cross modulation bridge 16 .and the receiver 11 is connected to the output terminal 18 of this bridge. `After detection in 19and filtering in 80 and 8| the'elevationinformation is displayed on a cross-pointer inl dicator 82.` range gate 83 coupled to the cursor .6- i on a .scope display may .be provided asinFig..2 to select a -desiredcraft ata given elevation. The operation of` the system is shown in` Fig.,A 9. When the aircraft: is on path, the upper antenf na 8 will receive no energy; hence there. will be no yinput to terminal 1|] of the upperbridge. The energy at terminal 69 will dividecqually .at terminals 12 Iand 13; thereby equal energy passes through each modulating section 14 and 15. After detection in 19 an on-path indication is obtained. When the aircraft is below path, the upper antenna will receiveV energy which is -phased and added to thatA of terminaltg, producing the sum at terminal 12 and the difference at terminal 13. Under these conditions, the Fl moduatin-g section 14 will be vfed more power than the F2 section 13, and the cross-pointer meter `82 will indicate that the aircraft is below the path When the aircraft is above the path, the upper antenna 8 will receive energy opposite in phase to that of the previous case. Hence terminal 13, will `deliver ,more energy thanterminal 121 and a predominance of F2 signal'will exist after detection, indicating the aircraft to the above path.`

The .antenna used in the transmission of the pulse energy from the ground station 9 can be separate'or as shown in Fig. 1 can'alsoactas an azimuth or `elevation receiving antenna. Furthermore the azimuth and elevation antennas maybe separate or comprise common elements as shown in Fig. l. Although the source of pulse energy has been illustrated as originating from a ground station in the vicinity of the ground receiving'` apparatus, the present system is capable of providing azimuth and elevation bearings of a landing aircraft if the aircraft itself is 'the source of original pulse energy.

It should be mentioned that 4actual modulation `of the pulses, radiated from'the craft, with subcarrier frequency energy may be feasible. In the present arrangement this beco-mes Iimpractical since the pulse would have to be very wide in order to accommodate several cycles of the subcarrier frequency modulations. However, Ain other arrangements, by closely spacing the two receiving antennas, vas for example, at the endof the runway, this latter mentioned method may be utilized.

While I have described above the principlesof our invention in connection with specific apparatus, rand particular modifications thereofit is to be clearly understood that this description fis made only by way of example and not as a limitation on the scope of my invention.

What is claimed is.:` l i,

l. Areceiving system for pulse energy radiated from a remote craftto b e guided along a prescribed course, comprising two antennas spaced apart transversely of said course, means for combining the pulse energy received by each of said antennas to provide sum and difference output components thereof, a source of separate moduf lation waves, means for separately modulating each of said component outputs with separate ones of said waves, means for combining said two modulated outputs, means for demodulating said twomodulated outputs to obtain the modulation componentsithereof, indicator means, and means for applying the modulation components to saidv indicating means for indicating theh` direction of said craft.

2. xA receiving system for pulse energyradiatfed from a remote' craft to be guided along af-preT .carrier-frequency .andsmounted `one on=y eachxside ceivedbyeachof said antennas, means for :com-

-bining said ldetected* components to-.provide su-m and difference component outputs thereoigmeans forfproyidinga. phase displacement .between each of .said componentwoutputs, a source ofjmodulaytion .ts/aves,y means for `applying said Waves in g'mengphase relationship for separately-'modulating .each of Vsaid vcomponent outputs after said phase V i'lisplacement, means for combining .said modulated outputs, means for demodulating said combined modulated outputs to obtainthe modulation components thereof, .indicator means, and meansl forwapplyingsaid modulation components to said-indicator `means forindicating the direction of said craft. .A receiving system for pulse energy radiated from-a remote craft to Vbe guided along a Drescribe d.course,comprising two antennas spaced apart a ygiven fraction of a wave length at a subcarrier frequency 'and` mounted one on each side offsaid. coursameansfor separately demodulating the pulses received by each of said antennas to obtain the sub-carrier frequency components thereof,v means for combining each of said demodulated outputs yto provide sum and difference component outputs thereof, means for Yproviding aphasedisplacement between each ofsa'id component outputs, a source of m-odulating waves, means for applying said waves in given phase relationship .for separately modulating each of` said combined outputs after said phase displacement,

means for combining saidtwomodulated outputs,

meansfor demodulating said combined modulated outputs to obtain the modulation components thereof, indicator means, `andrmeans for applying .the modulation components to said indicator mea-ns for .indicating the direction of4 said craft.

v4. An arrangement according t0 claim 2, wherein said phase displacement comprises a 90 phase displacement.

5. An v'arrangement according to claim 3,

wherein said phase displacement comprises a 90 phase displacement.

`6;` A receiving system for pulse energy radiated froma remote craft to be vguided along'a vpre-- scribed course 'comprising two antennas spaced 'apart a givenfraction of a wave. length at a subL carrier-,frequency andmounted one on each side of said course, means for separately receiving and demodulating the pulse energy received by each of said antennas'to obtain the sub-carrier components thereof, means for combining each of said demodulated outputs to provide distinct sum and-'difference component outputs thereof, means for providing a phase displacement between said component outputs, means for combining said component outputs after said phase displacement to provide sum and difference component outputs thereof, a source of separate modulation waves, means for modulating each of said last named sum` and difference component Aoutputs' with separate ones ofL said modulation waves, means for combining said `modulated waves, means for demodulating said modulated waves to'. obtain the modulation components thereof, in-

dicating means, and means for applying each of a.

said modulation components to said indicator meansvfor indicating the direction of said craft.

., 4`fl. l A. receiving-system for pulse energy radiated Imm'fa remotevcraftjto be guided .along a prescribed fcourse l, comprising two.v antennas yspaced thereof :means lfor providing .a phase iiidisplaicementusbletween saidu component outputs.; agfsonrce of v.separate .modulation fwaves, :means formodulatins;- one -of Vsai-d component outputs after @said phasevdisplacement with said modulation .waves of :a ,given phase, ,-meansfor deriving `two separate outputszfrom theother of. said component outputs after-saidlphasezdisplacement, means .for .madlilating, one V,ofsaid separate outputs, .and Vtl-ie-r1=itlier of @said separate l outputs being phase displaced and ;then-,modulated by separate ones,` of .saidv modulation waves, meanstfo-r combi-ninggqall Iof saidmodulatedoutputs, means for :demOdula-ting said combined outputs to .obtain the sub-,carrier components thereof, means vfor demodu-latingsaid sub-carrier .componentsgto `obtain the modulation components thereof, :indicator means, and means for` Aapply-ingh said modulation icomponents togsaid indicator f means v for indicating', they direction of said'craft. .l 'n K .8. ,A receiving system for puls'efenergy radiated from' a' remote .craft itofbe guided yalong apre'f scribedaglidepath -course,-comprising :two antennasspaced apart in the vertical a ,pluralityvv of Awave ylengths `at the ,carrier` frequency of said pulse .energy,y means. for combining they ,pulseen-L ergy .received by Veach of said. antennas to obtain sum and difference component ,outputs thereof, ,a sourceof separate modulation Waves,meansfor modulating each osaid component outputs With 4 separate ones of said modulation waves, means for combining .said .modulated outputs, means for derr'iodulating said combined 'modulated outputs f to obtain' the modulation components thereof, in-

dicating means, and means for applying'said modulation components to saidindicating means for indicating the direction ofsaid craft.

9. An arrangement as set Aforth .in 'claim 6,

wherein .said pulse energy radiated yfromsaid craft comprises reradiatedpulse` energy, means located at said .course for transmitting pulse'energy to said craft for reradiation from said' craft,

` a cathode ray oscillograph, a sweep generator for said oscillograph, means for applying a synchro- K nizing signal from said'source of pulse energyto controlthe Voperation of said sweepV generator, means for applying the output of one of said re,-

. ceivingmeans to control the indication of said os'.-

'cillograph, `a range cursor on said oscillographjan adjustable gating circuitA for controlling vfrelllase ofA energy to said means for demodulatingener'gy anda Amechanical coupling between said cursorv andl saidgating circuit. Y `ANTHONY 'CASABONA. f'

GUS STAVTLS.

- f- REFERENCES `CITED YIhefollowing references are of record in file lof. this patent.: 

